Infographics: COVID-19 in Alberta by the numbers

EDMONTON --
As the number of COVID-19 cases mounts in both Canada and Alberta, we're slowly getting a clearer picture of how the pandemic is spreading and how the situation here compares to other jurisdiction.

While the daily case count announcements from provincial health authorities are the most eye-catching figures, there's other important numbers beyond newly confirmed cases.

The number of patients hospitalized and in intensive care units gives a better idea of how the virus is taxing our health care system while also indicating how successful preventive measures have been.

Testing figures can also influence the number of announced new cases with sudden spikes in infection often related to a cleared glut of testing, rather than a series of outbreaks.

The above graph displays the number of total Alberta cases as well as deaths, hospitalizations, intensive care unit patients and recoveries.

Those categorized as "sick but not in hospital" are confirmed, active cases who haven't died, recovered or are in hospital or ICU. Note, the number of patients hospitalized does not include those in intensive care units.

Adding the number of sick (not in hospital), hospitalized (not in ICU), and ICU patients together results in the number of confirmed, active cases in the province.

Recoveries are defined by Alberta Health Services as follows:

A return to health after 14 days of isolation for those with COVID-19 but who experienced only mild symptoms.

If hospitalized due to COVID-19, anyone who does not require additional hospitalization or treatment in the 10 days after they left the hospital.

If tested, such as a health care worker, two negative tests at least 24 hours apart.

HOW IS COVID-19 GROWING AND SPREADING IN ALBERTA?

On March 23, the province announced that it was changing its testing policy and would no longer be checking returning travellers, who were instructed to self-isolate upon return as though they had contracted the virus.

Given that change, the number of travel-related cases has largely flattened since early April.

Close contact with individuals known to be carrying the virus remains the most common way of spreading COVID-19 in Alberta.

Suspected community transmitted cases, where the carrier isn't immediately known, are an important indicator of how the coronavirus is spreading in a community as well as how successful measures like physical distancing have been in limiting transmission.

"Every one of these cases is concerning, and we follow up with every case to ensure we are limiting spread," said Dr. Deena Hinshaw, Alberta's chief medical officer of health, on April 3.

"However, it does not seem at this moment in time that we are seeing a rapid rise in local transmission."

The sum of community-transmitted, travel-related and close contact cases doesn't necessarily equal the number of total cases as health authorities undertake investigations of varying time lengths into the cause of each individual case.

On April 4, the province began distinguishing between lab-confirmed and probable cases, though both are included in the daily announced new case counts.

HOW IS ALBERTA TESTING FOR COVID-19?

Alberta has now administered more than 200,000 tests for the coronavirus.

The province has made seven notable shifts in testing policy.

On March 23, the province announced it was focusing testing on at-risk populations and health care workers. At the same time, testing returning travellers was deprioritized to only those showing symptoms. Other travellers were instructed to self-isolate for 14 days upon returning to Canada.

Health authorities had indicated that not everyone who wants a test needs or will get one, and that some people are tested more than once.

On April 7, testing was opened to any symptomatic individuals in the Calgary Zone, which has been home to a majority of the province's cases since near the start of the pandemic.

On April 13, testing was expanded to any Albertan with symptoms consistent with the coronavirus.

On April 17, the province announced it would start testing all staff and residents of continuing care facilities for COVID-19 regardless of whether or not they show symptoms.​

On May 4, the testing criteria was expanded again to include anyone exeperiencing headache, muscle or joint aches, fatigue or severe exhaustion, nausea, vomiting, diarrhea, unexplained loss of appetite, loss of sense of smell or taste, or pink eye.

On May 11, the province opened testing to asymptomatic residents of the Calgary zone who work outside their home. Testing is to be done on a first-come, first-serve basis for up to 1,000 asymptomatic residents each day. The policy was in place until May 18.

And, on May 29, Dr. Hinshaw announced all Albertans, including those who are asymptomatic, were eligible to be tested.

Alberta has been the top province in Canada measured by per capita testing for the coronavirus since near the start of the pandemic.

HOW DOES COVID-19'S GROWTH IN ALBERTA COMPARE TO ELSEWHERE?

Conclusions drawn from comparing provinces are somewhat limited by widely differing testing volumes and practices among provinces, but the raw data does allow from some contrast.

The above graph ranks provinces by the number of tests they administer and how many confirmed cases they have, both measured per 10,000 population.

Tests are also not without their own biases. More tests will produce more positives, and it's easier to test everyone in a less populous province.

Rates adjusted for population provide a snapshot of the COVID-19 situation on any given day, but experts say the growth of the virus, unrelated to population size, is a more important indicator of the future.

The below graphs display Alberta's coronavirus curve alongside other provinces and other countries. Both use a logarithmic scale to better depict the exponential growth of COVID-19.

WHERE IS COVID-19 HITTING ALBERTA HARDEST?

COVID-19 cases have been found in every health zone in Alberta since mid-March.

The Calgary zone has seen the biggest balance of confirmed COVID-19 cases since the early days of the pandemic. The south zone had showed the slowest growth of new coronavirus cases, until an outbreak at a Brooks-area meat packing plant resulted in a sharp increase over April 21 and 22.

Sizable daily jumps in the new number of cases can't necessarily be attributed to the virus growing, as testing volume and reporting time also influence the data.